docs: def get_mmax(self, mfd_conf, msr, rake, area):
          '''
          Gets the mmax for the fault - reading directly from the config file
          or using the msr otherwise
  
          :param dict mfd_config:
              Configuration file (see setUp for paramters)
  
          :param msr:
              Instance of :class:`nhlib.scalerel`
  
          :param float rake:
              Rake of the fault (in range -180 to 180)
  
          :param float area:
              Area of the fault surface (km^2)
          '''
          if mfd_conf['Maximum_Magnitude']:
              self.mmax = mfd_conf['Maximum_Magnitude']
          else:
              self.mmax = msr.get_median_mag(area, rake)
  
          if ('Maximum_Magnitude_Uncertainty' in mfd_conf and
                  mfd_conf['Maximum_Magnitude_Uncertainty']):
              self.mmax_sigma = mfd_conf['Maximum_Magnitude_Uncertainty']
          else:
              self.mmax_sigma = msr.get_std_dev_mag(rake)